I'm not all that close to what's going on in JSF these days but as I see it, JSF is shaping up to be a very nice, iterative improvement over JSP development today and it applies a nice development policy, sort of a Struts-like development model to JSP development and it also gives developers a richer set of controls and a means of creating richer controls for Web browser-based experiences. But it is I think more like .NET WebForms in the sense that the baseline is still classic Web tier. The experiences are still delivered in a browser through html. There is a mechanism in JSF that can be extended and exploited to offload some server side processing to the client. So, using the renderkit mechanism, I expect developers will be able to use Flash among other technologies within JSF. But still the base model is one that involves request and response for documents on the server and the reconstruction of client-side state and all the things that go along with the classic Web tier model. So I think JSF could be used to create RIAs but its base model is not the creation of RIAs.